Many different types of sample handlers have been used in various analytical instruments to feed multiple test tubes into and out of the instrument. Several manufacturers have utilized a sample handler system whereby the sample handler comprises an input queue, an output queue and a cross-feed. The input queue consists of an area in which racks of test tubes are input into the instrument and are transported toward the cross-feed. The racks are then transferred to the cross-feed, where one or more racks may be at a given time. The racks are indexed at set positions along the cross-feed where operations are performed on the test tubes, such as aspirating samples from the test tubes, and the racks are then moved to the end of the cross-feed adjacent the output queue where they are output to the output queue. One such system is described in U.S. Pat. No. 5,207,986. Various methods are used to transport the racks within the input queue and output queue. In some instruments, like the Chem I system sold by the Bayer Corporation, the input queue and output queue are indexed and walking beams are used to lift the base of the racks and translate them from one indexed position to an adjacent indexed position.
It is desirable to provide a sample handler that handles containers of various types, diameters and heights, whether capped or uncapped, and to permit a robotic arm to transport the containers to and from the sample handler for faster processing elsewhere without have to return the containers to a particular rack or position on the rack.
These prior art instruments do not provide this flexibility. First, they only handle a single type and style of test tube within a particular instrument. Second, these sample handlers are not designed to work in conjunction with a robot that removes containers, such as test tubes, individually from the racks for transport either within the instrument or between the instrument and a laboratory automation transport line. An entire rack would likely be lifted if a robot were to attempt to lift a test tube from a rack in the prior art instruments. Third, the input queue and output queue generally are not designed to handle uncapped test tubes because they do not stabilize the racks sufficiently and samples in open test tubes may spill. Fourth, the positions of the test tubes within a particular rack must be maintained or the instruments will be unable to track and perform the proper operations on the test tubes.